Water Pump

[Rickross]

Does anyone know what the cylindrical part of the 8.1s Horizon water pump does? I replaced impeller on starboard engine, re-attached hoses and I can’t get the water shooting out the side of boat, I actually pulled the pump twice (to review my work) as it didn’t work the first time, and it’s not working now.
Hoses connected correctly.
Impeller and o-ring in the housing seated correctly.
Sea cock open.
Sea strainer full of water.
What am I missing?

 

[Wanderer 290]

Is the the pump clocked properly? Upon installation if the pump housing is rotated 180* the inlet/outlet flow is effectively reversed.

 

[Rickross]

Wanderer 290, We are pretty sure everything is assembled properly, checked and double checked

 

[R-and-R]

Is there any scoring/wear on the inside of the housing?
The impeller needs to mate to flat surfaces to function properly. If there’s inefficient seal, priming it may help getting the water flowing.

 

[Wanderer 290]

Does the engine overheat if if left to run for a few minutes?

 

[Rickross]

There is some slight scoring and it ran good prior to the impeller change. We also didn’t let the engine run long enough to over heat. We did let it run for about 1 to 1.5 minutes and still no water pumped out. We also put a garden hose into the line feeding the pump. It seem to pump at about 75% with the hose in then petered out to a very slight dribble.

 

[R-and-R]

If your pump and impeller are in good condition, it shouldn't need priming. But before I rebuilt my pumps with stainless steel plates, I would normally have to prime mine due to scoring and incomplete seal between impeller and pump housing.

You might try this to make sure the pump is primed. Remove the raw water hose at the input side of the transmission fluid cooler.
Pour about 2 gallons of freshwater into that hose. It will flow down to the outlet side of the pump and fill the pump with water. The water level in that hose won't fill up, it will drop down to water line level, but it should keep the raw pump filled/primed. Reconnect hose and start it.
If that doesn't fix it, I'm out of ideas.

Good luck.